The presence of dissolved gases, even in small amounts, is undesirable in systems having aqueous solutions which contact metal surfaces. "Aqueous solutions" as used herein includes solutions in which water is the predominant component as well as solutions in which water is present as a minor component along with predominantly hydrocarbons. Such solutions include crude oil and water solutions produced from oil bearing subterranean formations. Metal surfaces in contact with oxygen-containing aqueous solutions can experience pitting. Pitting is highly concentrated corrosion affecting only a small area of the total metal surfaces. Pitting can be a serious problem causing metal failure even though only a small amount of metal is lost and the overall corrosion rate is relatively low.
The severity of attack by oxygen will depend on the concentration of dissolved oxygen in the aqueous solution, pH and temperature. As aqueous solution temperatures increase, as for example in a water heating system, enough driving force is added to the corrosion reaction that small amounts of dissolved oxygen in the aqueous solution can cause serious problems. Oxygen pitting is considered to be a very serious problem in systems such as pipelines, boilers and aqueous heat exchange systems such as boiler feedwater heaters, economizers and superheaters.
In some systems such as boiler systems, vacuum deaeration is an important first step in removing dissolved oxygen in water along with the addition of chemical corrosion inhibitors. In other systems such as pipelines, chemical corrosion inhibition is the typical means to inhibit oxygen induced corrosion.
Due to the variety of systems where oxygen induced corrosion is a problem, a continual need exists for new, effective, chemical corrosion inhibitors.
Thus it is an object of this invention to provide compositions and methods of using the compositions which are effective for inhibiting oxygen induced corrosion of metals exposed to aqueous solutions.